Many devices that require electricity from a battery are limited in usefulness by the battery's lifetime. Both weight and size (in other words, energy density) can be limiting factors on battery life, particularly for small devices. In particular hearing aids and many other devices would be enhanced by increasing the battery's energy density. For example, many devices could be further miniaturized if a smaller battery that gave reasonable energy density were available.
Accordingly, there is a general need to generate as much electrical energy as possible from a battery having a limited volume.